VORTEX INDUCED VIBRATION MITIGATION METHOD AND SYSTEM

Abstract

Systems and methods for suppression of vortex induced vibration (VIV) in subsea conduits are disclosed, as may be used in oil and gas, carbon capture and storage, subsea mining or any other subsea operations where multiple conduits extend between a floating vessel and the sea floor and are subjected to VIV causing currents. VIV suppression elements may be wrapped around one or multiple conduits, and along their entire length or in regions where VIV effects are anticipated. The suppression members may also help to alleviate damage due to clashing of the conduits under the influence of the water currents.

Claims

1. A system comprising: one or a plurality of fluid conduits extending from a vessel located above a well location and extending from the vessel through open water to the subsea well location; vortex induced vibration (VIV) reducing members, a VIV reducing member being wrapped around each of the fluid conduits; a control and communication umbilical extending from the vessel to the subsea well location; and a wireline extendable and retractable from the vessel to the subsea well location independently of the fluid conduits and the control and communication umbilical.

2. The system of claim 1, wherein the VIV reducing members are wrapped in the same direction on the fluid conduits.

3. The system of claim 1, wherein the VIV reducing members are wrapped in opposite directions on the fluid conduits.

4. The system of claim 1, wherein the control and communication umbilical is disposed adjacent to a first of the fluid conduits and is wrapped together with the first fluid conduit by a common VIV reducing member.

5. The system of claim 1, wherein at least a first of the fluid conduits is wrapped by two VIV reducing members, the two VIV reducing members being wrapped in opposite directions on the first fluid conduit.

6. The system of claim 1, wherein a plurality of control and communication umbilicals or a plurality of fluid conduits are wrapped together by a common VIV reducing member.

7. The system of claim 1, wherein at least one of the VIV reducing members comprises a fluid or electrical control or communication conduit.

8. A system comprising: a fluid conduit extending from a vessel located above a well location and extending from the vessel through open water to the subsea well location; a vortex induced vibration (VIV) reducing member wrapped around the fluid conduit; a control and communication umbilical extending from the vessel to the subsea well location independently of the fluid conduit; and a wireline extendable and retractable from the vessel to the subsea well location independently of the fluid conduits and the control and communication umbilical.

9. The system of claim 8, wherein the VIV reducing member comprises a fluid or electrical control or communication conduit.

10. The system of claim 8, wherein the control and communication umbilical is also wrapped by a separate VIV reducing member separately from the fluid conduit.

11. The system of claim 8, wherein the VIV reducing member is wrapped in a generally helical configuration with a pitch of between approximately 6 inches and 4 feet.

12. The system of claim 8, wherein the VIV reducing member comprises a substantially round cross-section having a nominal diameter of between approximately inch and 1.5 inches.

13. The system of claim 8, wherein the VIV reducing member comprises a substantially flat tape-like material.

14. The system of claim 13, wherein the VIV reducing member comprises a reinforcing element within or adjacent to the tape-like material.

15. The system of claim 8, wherein the fluid conduit is wrapped by two VIV reducing members, the two VIV reducing members being wrapped in opposite directions along the fluid conduit in similar or intentionally different pitches.

16. The system of claim 15, wherein the two VIV reducing members are wrapped in generally helical configurations having substantially the same pitch or differing pitches to create intentional overlap.

17. The system of claim 8, wherein a ratio of a diameter of the VIV reducing member to a diameter of the fluid conduit is between approximately 1:4 and 1.15.

18. A method comprising: separately wrapping a plurality of fluid conduits, one of which may be a rigid riser, with respective vortex induced vibration (VIV) reducing members, the fluid conduits, when deployed extending from a vessel located above a well location and extending from the vessel through open water to the subsea well location; extending a control and communication umbilical from the vessel to the subsea well location independently of the fluid conduits; and extending a wireline extendable and retractable from the vessel to the subsea well location independently of the fluid conduits and the control and communication umbilical.

19. The method of claim 18, wherein the control and communication umbilical is also wrapped by a VIV reducing member separately from the fluid conduits.

20. The method of claim 18, wherein at least one of the VIV reducing members comprises a fluid or electrical control or communication conduit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings described below in which like numerals refer to like parts.

[0013] FIGS. 1A-1C are a diagrammatical depictions of applications, such as subsea well applications, illustrating the inventive system employed to reduce vibration and movement of conduits extending from a vessel to a subsea location;

[0014] FIGS. 2A-2E are diagrams illustrating effects of vortex shedding resulting from sea currents, as well as effects on the profile of conduits extending through deep water in which various currents may be present;

[0015] FIGS. 3A and 3B are diagrammatical illustrations of presently contemplated exemplary embodiments for wrapping a conduit, such as coiled tubing, in a manner to suppress or reduce vibration and movement from vortex shedding;

[0016] FIGS. 4A-4I illustrate presently contemplated exemplary wrapping arrangements for use in the system;

[0017] FIGS. 5A-5C illustrate certain of the design considerations for the system;

[0018] FIG. 6 illustrates one of many other possible uses of the system, in this case a subsea jumper; and

[0019] FIG. 7 illustrates exemplary operations for implementing a system for reducing or suppressing vibration and movement in subsea conduits.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0020] Turning to the drawings, and referring first to FIG. 1, a (VIV) suppression system is illustrated and designated generally by the reference numeral 10. The system is shown in an application wherein a seagoing vessel 12 floats on a body of water 14 above the seabed 16. In practice, any other suitable application may be envisaged, including on movable or stationary platforms, rigs, ships, and so forth. The depth of the water may vary widely in such applications, from hundreds to thousands of feet. The vessel will be positioned above one or more wells 18 which traverse various geological zones, and in particular a zone of interest 20 which may contain minerals (e.g., oil and/or gas) to be extracted or a reservoir for the storage of captured carbon dioxide, for example. An opening 22 in the vessel, sometimes referred to as a moonpool may allow for various conduits to be extended from equipment 24 on the vessel. By way of example, such conduits may comprise coiled tubing 26 stored on one or more reels 28 on the vessel (or on a dedicated delivery and support vessel, not shown). Such coiled tubing will normally be associated with specialized equipment for its deployment and retrieval, such as a gooseneck, an injector, a clump weight, and a straightening and control system including injector chains and an exit guide (not separately shown in the figures but known by those skilled in the art). Flexible jumpers (discussed below) may be provided on lower ends of coiled tubing sections to allow them to be attached to the well equipment. In anticipated applications, where coiled tubing is to be protected from adverse effects of VIV, lengths of tubing on the order of 14,000 feet or more may be stored and deployed as set forth below.

[0021] In the illustrated embodiment the vessel and its equipment may be designed for intervention at the well, though a range of applications for the present techniques are envisioned. Interventions may involve temporary operations required from time to time, while other applications may include, for example, risers (both for drilling and production), both permanent and temporary risers and umbilicals (e.g., for control and/or communications), remote operated vehicle control lines and tethers, jumpers, and so forth. Further, though the use on coiled tubing is discussed most extensively here, the system may also be used on cables, hoses, pipe, and sheathed and unsheathed sets of conduits, designed for both fluids, electrical power and electrical or optical signals.

[0022] Returning to the figure, also shown are other conduits designated generally by the reference numeral 30, but that may differ substantially both physically and functionally. These may include, for example, hydraulic control hoses (e.g., for control of valves in the wellhead equipment), electric power conductors for powering motors, valves and other equipment, communications lines for providing control and feedback signals between the vessel and the wellhead equipment, and so forth. In some embodiments, all or some of these may be combined in a sheath or other grouping arrangement. Prior to deployment or after retrieval these may be stored in one or more reels as indicated simply by reference numeral 32. Of course, such reels will be provided with machinery for their powering and control (not separately shown).

[0023] In addition, in the illustrated embodiment a wireline 34 is provided that is stored on a separate reel 36. Here again, the wireline and its reel will be associated with dedicated equipment for controlling its deployment and retrieval (not separately shown). As will be readily appreciated by those skilled in the art, such wirelines may be relied upon for any number of important operations in the well, such as the placement, movement, and retrieval of components within the well. In the present context, it may be desired to maintain the wireline separately and independent of the other conduits to which the VIV suppression techniques are applied. This will allow the wireline to be freely used while the other conduits remain in connection with the wellhead equipment.

[0024] As shown in the illustrated embodiment, one or more of the conduits will be wrapped in a way that will suppress, eliminate, or reduce VIV, as indicated generally by reference numeral 38. Particular arrangements for such wrapping are discussed in much more detail below. From the vessel 12, the various conduits extend to the wellhead structure 40. As will be appreciated by those skilled in the art, such structures will include various arrangements of valves, sometimes referred to as a Christmas tree that allow for opening and closing the well, inserting and retracting equipment in the well, injecting various fluids, detecting well conditions, and so forth. In the illustration, a subsea riserless light well intervention (RLWI) system 42 is shown atop the well structure, and may be installed temporarily, such as to receive the wireline 34. A pressure control head 44 is shown at the top of the RLWI system, which is connected through the RLWI system to the conduits 30 (e.g., umbilical). Two lengths of coiled tubing (or flexible hose) are also connected to the RLWI system for fluid and/or gas circulation purposes. The coiled tubing may terminate in flexible jumpers 46 as mentioned above, to facilitate connection to the control head. Where desired, a clump weight 48 may be provided to create a downward biasing or stabilizing force on the tubing. In practice, the lines may be made up to the well structure and serviced as needed by remote operated vehicles (e.g., remotely controlled robotic machines), not shown in the figure.

[0025] When deployed as shown, the various conduits may be within fairly close proximity to one another, and that over a very considerable length. For example, the moonpool through which they exit the vessel may be on the order of 10 to 30 feet wide, while at the wellhead, the lines necessarily come close to one another, particularly at their points of connection and just above the wellhead. Because the well may be in very considerable depths, as mentioned above, and because the conduits are essentially unconstrained along their length, they will move with movements of the vessel (if any), but primarily owing to water currents, as indicated generally by arrows 50 in the figure. Some of these currents may be known or anticipated in some applications, but very considerable variation may be encountered both over time, and in particular locations where the system is used. Moreover, substantial differences in the currents may be seen at different depths.

[0026] FIG. 1B illustrates a similar application, but in which circulating lines that connect to the subsea RLWI stack do not pass through the moonpool, but instead go over the side of the vessel and connect to the stack subsea. FIG. 1C, on the other hand, shows another application in which the vessel 12 comprises a semi-submersible with a rigid riser and associated choke and kill lines attached to the riser, and the VIV reducing member is wrapped around the riser assembly. Here reference numeral 38 designates a fluid circulation line, while reference numeral 38 designates a drill pipe riser or small bore intervention riser. In such applications, the VIV reducing system may be wrapped around the riser and/or the circulation line.

[0027] FIGS. 2A-2E illustrate some of the movements that may be encountered by the conduits and that are addressed by the present techniques. These techniques recognize that the VIV problem may be the result of strong subsea currents, including loop currents, may cause coiled tubing and other conduits to vibrate back and forth vigorously, inducing fatigue in the tubing, particularly immediately below the injector head where the tubing exits the vessel and enters the sea. Such VIV is illustrated in FIGS. 2A and 2B. Separate conduits 52, 54, and 56 may experience individual vortex shedding phenomena as illustrated by curved pressure arrows 58, 60, and 62, respectively. Such vortices will may result in vibrational motion of the conduits, as indicated by reference numerals 52, 54, and 56, respectively. FIG. 2A generally represents the unconstrained situation of the prior art in the face of sea current VIV. FIG. 2B represents a conduit 66 that is wrapped by a VIV suppression member 68 as discussed herein. Despite the same currents, then, it is believed that vortex shedding and its consequent vibratory effect on the conduit is substantially reduced or eliminated, as indicated by smaller arrows 70 in the figure. In practice, the VIV experienced by the conduits may be quite small in amplitude, but still potentially critically damaging to the structural integrity of the conduits. The technique illustrated in FIG. 2B, then, may prove highly useful in prolonging the life of the conduits, which in some cases are used over and over on different wells. In general, a goal of the present techniques may be to disturb laminar flow around the conduits, or to otherwise interrupt the periodic pressure fluctuations that induce the vibrations from vortex shedding.

[0028] And it should be borne in mind that these detrimental effects of currents may occur differently at different depths of water, as shown generally in FIG. 2C. In this figure, from the sea surface (where the vessel will be located), the conduits may encounter different currents 74, 76, and 78 at these different depths, and these may also vary over time. As a consequence of such currents, the conduits may assume different configurations or profiles, as indicated by broken lines 80, 82, and 84. Here again, each of the essentially independent and free conduits may assume its own profile, and these may be continuously changing. And these profiles may move in three dimensions as the currents change. Such profiles, in addition to the adverse effects or VIV, or in some case in combination with them, may cause clashing between the conduits.

[0029] Finally, as shown in FIGS. 2D and 2E, the conduits may be either relatively unconstrained or constrained as they exit the vessel. FIG. 2D illustrates a relatively unconstrained situation in which an upper end 86 of the conduit may move relatively freely in the moonpool, and may assume different shapes 88, with an overall movement range indicated by reference numeral 90. FIG. 2E represents a situation in which an upper end 92 of the conduit is constrained, such as by an exit guide of the deployment equipment. From this point, the conduit will bend in a manner similar to a single end fixed beam, and assume different profiles 94, again within a range of movement 96. As will be appreciated by those skilled in the art, in the latter case, VIV effects on the integrity of the conduit may be greatly exacerbated, particularly in the region just below the constraint. For this reason, in some embodiments, it may be desirable and sufficient to wrap one or more of the conduits (as discussed below) over less than their entire length, but in particular regions of increased risk from VIV, such as along an upper length where the conduit(s) exit the vessel.

[0030] The present techniques allow for suppressing the VIV by wrapping one or more of the conduits with one or more members that change the fluid dynamic characteristics of water moving from an upstream side of the conduits to their downstream side. In some embodiments, it may be desired to wrap more than one, and in some cases all of the conduits separately or in some combinations (e.g., coiled tubing lines individually, and combined control and communication lines together). The wrapping may be performed prior to deployment of each line, and in a presently contemplated embodiment, this is done as the lines are unreeled and just before they enter the sea. They may be unwrapped in a reverse operation as they are retrieved following a temporary use (if applicable).

[0031] FIGS. 3A and 3B illustrate one presently contemplated VIV suppression wrapping approach. As shown, a coiled tubing deployment system 98 may include controlled chains or other structures that contact the tubing 26 and control its removal from its storage reel, with some degree of straightening, before lowering it into the sea. Here the VIV suppression system may include a reel 100 on which a VIV suppression wrapping member 102 is stored. A guide structure 104 allow controlled removal of the member 102 and guides its wrapping around the tubing in a generally helical arrangement as it descends. The reel 100 or the guide structure 104, or both, may be driven in rotation, as indicated by arrow 108, and at a rate coordinated with the movement of the tubing, so as to provide a consistent pitch to the helix defined by the wrapped member. By way of example, in one contemplated embodiment, 0.4 inch (10 mm) polypropylene rope could be used as the VIV suppression member, and would be wrapped on a 10,000 foot length of coiled tubing (e.g., resulting in wrapping approximately 14,000 feet of rope). The winding mechanism may include a reel having a drum core of 3.2 feet, 4.8 foot end flanges, and a drum width of 1.6 feet. The guide structure maintains tension to pay out or wind in the rope. The figures show a drum positioned axially around the downline of tubing, paying out and winding in the rope through a level-wind type mechanism and wrapping it around or unwrapping it from around the downline. Equally, the drum could be a cylinder which is positioned radially from the downline with its axis perpendicular to the downline and rotating around the downline as it pays out and winds in the rope.

[0032] In some presently contemplated embodiments, rather than rope the VIV suppression member may comprise a power cable, a communications cable, a fiber optic cable or any combination of these, enabling the transmission of power and communications simultaneously to the suppressions of VIV. Where multiple conduits (e.g., lengths of coiled tubing) are to be wrapped, different VIV suppression members may be used for each, with some or all of these being control (e.g., hydraulic and/or electrical) and/or communications conduits. Equally, the cables could be wrapped around the downline to gain support while providing power and/or communications even when VIV suppression is not required. As mentioned above, the conduits receiving the VIV suppression member may be other than a single conduit, but rather may comprise multiple conduits combined or ganged, such as in sheaths.

[0033] FIGS. 4A-4I illustrate some exemplary embodiments of VIV suppression wrapping. As shown in FIG. 4A, a single member 110 may be wrapped helically around a conduit 26. Here the pitch of the helical wrapping is maintained generally constant, but in some embodiments it may be useful to vary or even control the pitch to be different in different regions of the conduit, such as in a region where the conduit exits the vessel. FIG. 4B shows an embodiment in which two wraps 110 and 112 are used, these being wrapped in opposite directions with respect to one another. Here again, the pitch of these two wrapped VIV suppression members may be the same (as shown) or different, and the pitch of one or both may be varied in a controlled way along the length of the conduit of most concern.

[0034] FIGS. 4C and 4D represent VIV suppression wrapping in which additional elements are incorporated that may further aid in addressing concerns with both VIV and clashing of the conduits with one another. FIG. 4C illustrates a series of bumpers 114 installed along the VIV suppression member, while FIG. 4D shows a different type of bumper or spacer that may be pre-installed on the VIV suppression member. In both cases, the devices may be used over the entire length of the VIV suppression members, or just at locations of particular concern (e.g., where clashing is more likely).

[0035] FIGS. 4E and 4F illustrate one of a variety of alternative configurations for a VIV suppression member, in this case, a generally flat or tape-like structure 118. Such structures could be made of various materials compatible with the environment in which they are to be deployed, such as an elastomer. In the illustrated embodiment, a reinforcing element 120 is shown in the tape-like structure. Such elements could be either embedded in the structure, or be located immediately adjacent to (e.g., under) the structure, such as between the structure and the conduit. In some embodiments, such reinforcements may comprise wire or cable. Alternatively, the embedded or adjacent element could be a control and/or communication conduit, or multiple of these.

[0036] FIGS. 4G-4I represent a further alternative in which two (as shown, though this could include more than two) conduits are disposed adjacent to one another and wrapped with a common VIV suppression member. In such cases, one or more clamps or binders 24 may be used at desired locations along the length of the conduits, and then a VIV suppression member 126 is wrapped around the bundle of conduits. The illustrated arrangement may be considered a combination of a primary conduit (e.g., coiled tubing) and a secondary conduit (e.g., a control conduit or hose). The latter may also be wrapped, or may extend generally linearly parallel to the primary conduit. Here again, the VIV suppression member may be any suitable material, such as rope, tape, or even itself a control or communication line.

[0037] FIGS. 5A-5C illustrate some of the potential design considerations for wrapped VIV suppression members in accordance with the present techniques. As shown in FIG. 5A, the system may first consider the depth or length 128 of the conduit to be protected, as well as its anticipated range of motion 130. Also, the system may consider one or more regions of particular interest over which the VIV suppression member will be used (possibly to the exclusion of other regions), as indicated by reference numerals 128 and 128 in the figure, that is, at upper and lower ends of the conduit. As noted above, it may be that higher VIV effects are anticipated, or that the risks to the integrity of the conduits are highest in such regions, and so they should be particularly protected. It is presently contemplated that the system could be used over lengths (or water depths) of between approximately 150 feet and 10,000 feet, for example, or along regions of as short as 25 feet.

[0038] As shown in FIGS. 5B and 5C, other considerations may be the diameter of the conduit(s) 132 as well as the pitch 134. In presently contemplated embodiments, such conduit diameters may range between approximately 1 inch and 36 inches, for example, though it should be borne in mind that this may be a single or multiple conduits (as in the case, for example, of combined or bundled control and/or communications conduits). Pitches presently contemplated may depend upon the diameter of the conduit, but may range between approximately 6 inches and 4 feet, for example. FIG. 5C again shows the design consideration of the outer dimension 136 of the conduit, though also of interest may be its wall thickness 138, or some ratio of these. Such considerations, possibly along with the particular material may guide the response to potential VIV, particularly in regions of interest of the conduit. Presently contemplated conduit dimensions may range between approximately 1 inch and 36 inches, with conduit material wall thickness ranging from solid to approximately 2 inches. Also, the dimensions and size of the VIV suppression members may be a key design consideration. FIG. 5 illustrates a round element, such as rope, having a nominal diameter 140. A system design may consider a range of sized and physical configurations, such as inches to inches. In some cases, ratios of sizes of the VIV suppression member and conduit may be established, but larger conduits receiving correspondingly larger VIV suppression members.

[0039] As noted above, the present techniques are not limited to any particular conduit or application, but may be used in temporary or permanent applications, such as for drilling, production, intervention, and so forth. FIG. 6 illustrates just one example of a permanent use in which a jumper 142 is installed between two wells 144 and 146. Such jumpers may be subjected to currents 50 that can cause VIV related ill effects. Accordingly, the present disclosure contemplates VIV suppression members 148 on these structures as well. In some cases, the VIV suppression members in such applications may be permanently installed with considerations similar to those outlined above.

[0040] FIG. 7 illustrates exemplary operations for implementing a system for reducing or suppressing vibration and movement in subsea conduits. The method 150 begins with preparation of the conduits to be protected, as noted at operation 152. As noted above, these may include coil tubing wound on large reels, and fed through straightening and controlled deployment equipment on one or more vessels. Other conduits may include control and/or communications conduits, which may be grouped into one or more umbilicals, and where desired may be bound together, such as in sheaths.

[0041] Operation 154 involves preparation of the VIV suppression wrap(s). Here it should be again noted that one or multiple of the conduits may be protected, and in some embodiments at least those likely to experience the worst effects of VIV will be wrapped. VIV suppression members will be prepared in this operation for all such conduits, with wrapping or winding structures for each. In some cases where only a portion of the conduits in specific regions are to be protected, this operation may include selective preparation of the VIV suppression member(s) according to what portion or region of the protected conduits is then being deployed.

[0042] Operations 156 and 158 may generally occur simultaneously and in coordination with one another. That is, as the conduits are being deployed, respective VIV suppression members may be wrapped around them in a manner consistent with the wrap specifications of the system (e.g., based on the considerations outlined above). It should be noted, however, that where only certain regions of one or more conduits are to be wrapped, these operations will be coordinated accordingly, such that the wrapping of operation 158 will only occur as those regions of the conduits are being deployed. Also, in some cases the conduits may be deployed successively such that only the one or ones then being deployed will be wrapped. This may allow for the same wrapping or winding equipment to be used for the different conduits, one after the other.

[0043] At operation 160, then, the conduits are made up to equipment on the vessel and the well, in accordance with existing technology, such as via one or more remote operated vehicles. Though not separately shown, retrieval of the conduits and VIV suppression members may follow the reverse order of operations. In some cases, some or all of the VIV suppression members may be kept for re-use.